Solid oxide cells can be operated in either an electrolysis mode or in a fuel cell mode. In an electrolysis mode, electricity and steam are supplied to the cell which then decomposes the steam to form hydrogen and oxygen. In the fuel cell mode, the cell operates in the reverse, burning a fuel such as hydrogen or methane to produce heat and electricity. When standard solid oxide cells are operated in an electrolysis mode, they characteristically respond to increases in water vapor partial pressure with an increase in the over-potential. As a consequence, higher driving voltages are required at high water vapor partial pressures. This means that the cell is less efficient because more voltage is required at a given current in order to produce a given amount of hydrogen and oxygen. A similar effect is noticed when the cell is operated in a fuel cell mode as the increased over-potential (i.e., an increased voltage drop within the cell) results in less electricity being produced for a given amount of fuel.